


Bittersweet Dreams

by tsukithewolf



Series: Universe Hopping [2]
Category: Undertale (Video Game)
Genre: Ambiguous gender Frisk, Can be read alone but makes a lot more sense if you read "A Tale of Two 'Verse" first, Demisexual Sans, Dream Sex, Human Sans didn't just get over that shit, Kind of a stupid ending, Other, Porn, REALLY BAD PUN, Straight up sin, Takes place after the first chapter of "A Tale of Two 'Verses", sin - Freeform, slight angst
Language: English
Status: Completed
Published: 2016-03-27
Updated: 2016-03-27
Packaged: 2018-05-29 12:56:22
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,585
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6375640
Author URL: https://archiveofourown.org/users/tsukithewolf/pseuds/tsukithewolf
Summary: <blockquote class="userstuff">
              <p>It's not easy to get over someone that quickly. </p><p>(A story that takes place after "A Tale of Two 'Verses".)</p>
            </blockquote>





	Bittersweet Dreams

**Author's Note:**

> A one-shot fanfiction because I ship Frisk hard with pretty much all forms of Sans. I wrote this a long time ago but decided "fuck it" and I'll post it here.
> 
> (Any confusion can be attributed to the fact that it is a dream. Beware of random scene changes.)

There were eggs cooking in the kitchen. How Sans knew that, he didn’t care, but he knew that there were eggs cooking in the kitchen. His stomach growled as he approached the kitchen and was delighted to find Frisk there. The human Frisk, his mind curiously supplied. He pushed the thought away because of course Frisk was human. Sans wasn’t one for eggs, but they smelled delicious to him. He could eat just about anything right now.

His eyes trailed down Frisk’s form, finding that they were only wearing an apron. A strange choice for cooking breakfast, but definitely not one that Sans was against. He felt no shame as he took in the view, allowing his eyes to linger on Frisk’s bum. He was half-tempted to decide to have something else for breakfast...but maybe Frisk would be up for both?

“hey.” He called, and Frisk turned their head. Their face lit up at the sight of him, and something in Sans’s chest ached pleasantly. 

“Sans.” Frisk greeted happily and turned to face him fully. It was a little sad to see the view change, but he was more drawn to their face than their body at the moment. Frisk glanced at the pan where the scrambled eggs were cooking. Sans approached them and hummed at the sight of the eggs. He then faced Frisk again, giving into the urge to kiss them. Frisk made a small surprised noise in their throat before abandoning their cooking to wrap their arms around Sans’s neck. Sans had only meant for it to be just a quick peck, but he took the opportunity in front of him. 

Frisk opened their mouth and allowed Sans to deepen the kiss. His hands ran down their sides as he gloried in the feeling of pressing against their body. The apron did little to hide the curves of their body. Sans wasn’t sure he would ever get over his need for Frisk. He ached for them constantly despite them living with him. It was almost not enough, having them in his bed or in his arms or in his life. 

“That’s why we got married.” Frisk murmured against Sans’s lips, kisses brushing across his stubble to press into the hollow of his ear. He shuddered a little. That was right. He glanced down at their linked fingers seeing the ring on Frisk’s finger catch the sun. He thought that he had chosen well with that ring. It represented their life together, and the one they would continue to share. Sans hadn’t been sure he would ever marry, mostly because he hadn’t been able to imagine who he would fall in love with. But how could he have expected Frisk to appear so unexpectedly into his life? He was thankful for it, though. He loved having someone to share his bed with. 

“heh, that’s right.” Sans said, somewhat distracted by the biting on his neck. He tilted his head to the side, feeling Frisk marking him. His free hand scratched a little roughly up their back, causing them to arch into him. He became aware of his growing erection. Well, that’s one way to start a morning, he decided. He considered how he wanted that to be taken care of. 

Frisk’s hand drifted lower over his thin shirt to cup him through his loose pajama bottoms. He leisurely pressed into their hand, humming around kiss and tongue that he had suddenly captured. Frisk pulled back as Sans stared into their heavy-lidded eyes. He could see the signs of arousal there: the swollen lips, the expanded pupils, the restless body. There was so much Frisk wanted to do, and so much Sans would let them do to him. 

Frisk’s hand was still on his crotch. They glanced down at it, squeezed a little, and then looked up at him through their eyelashes. They seemed almost shy if it wasn’t for the devious glint of their eye. A grin pulled at Sans’s lips as he licked at them. He felt anticipation build in him.

But Frisk turned away back to the grill. They were outside, after all, and it wouldn’t do to have sex in the backyard. No matter how hot that would be. Still, Sans was left discontent. He huffed his disappointment, watching Frisk’s hips as they sashayed their way back to the eggs. Frankly Sans no longer wanted food. He captured his partner, wrapping his arms around their waist and pressing his face to the juncture of their neck.

“can i make a change in the menu?” He mouthed against their pulse. He could feel it pounding against his lips. “maybe instead of eggs, you can have,” he pressed his hips to their bottom, “sasuage?”

There was only a split hesitation before the both of them were laughing. Sans buried his face in their neck to muffle his laughter while Frisk covered their mouth in their own effort to muffle themselves. Sans pulled their hands away, wishing to hear their giggles. Oh god, that was terrible. He loved that Frisk honestly loved his jokes. 

Frisk spun around in his arms, grabbing at his hips. “I don’t know...” They murmured. Their eyes were still alight with mirth, “does it _meat_ my expectations?” They slid down his front to drop to their knees. His sleep pants did nothing to block the hot moisture from their mouth as they kissed and licked the fabric. His head fell back as he half collapsed against the wall.

Goddamn, this kid was good.

Frisk’s hands snaked around to grab two handfuls of Sans’s bum. He jumped at the touch as Frisk muttered, “Sausage and buns.” He snorted at their joke and they grinned, proud, before they yanked down his sleep pants and underwear. He muttered a curse at the sudden exposure. They were in the backyard where anybody could see them. According to his body, though, this was apparently a good thing because he felt his blood rush south at the thought. 

Frisk moaned softly at the sight as Sans licked his lips hurriedly. They were so close to where he wanted them. But Frisk was teasing him. Their hands danced up and down his trembling thighs, sensitizing them. They pressed a kiss against the thin skin beside his cock. He tilted his head back and pressed a hand to their cheek, urging them to where he wanted them. Frisk complied, licking a thin trail up to his head. His hips jerked forward as he groaned.

“Careful.” Frisk warned, that devious look once again in their eyes. “The neighbors will hear.”

Sans muttered under his breath in Wing Dings. “stop being a tease then.”

Frisk wrapped their lips around his head and gave a quick suck. He gasped, hips bucking again. Frisk pressed them back to the wall again. Sans could feel his body shaking with the need to pound into that mouth. He wanted them to suck him, but he also wanted to push them down and capture those lips for his own again. He wanted them everywhere at once, and none of it seemed realistic right now. Frustration built in him, distracting him as Frisk’s hands and mouth worked him. 

“fuck fuck fuck!” He mumbled, grabbing a hold of their head. They held still for him as he pressed into their mouth. For just a moment he was suddenly back in his bed again, pushing into them for the first as their body lowered onto his. He could still feel the tingle of their orgasm against his lips and the taste of them on his tongue. The feeling of them pulsing around his fingertips was almost enough to finish himself off, but it wasn’t enough. It wasn’t realistic enough. He needed more.

“frisk.” He called, and they stopped to look at him. He wiped the saliva from their chin and pulled them up and into his arms. “frisk.” He murmured again, kissing them. And Frisk melted into the kiss. Their fingers pressed to his ribs and ran up his chest. He could taste himself in their mouth and it only drove him wilder. He couldn’t stay standing.

Sans grabbed their thigh and hefted it up onto his hip before pressing them back against the desk. Frisk happily shifted onto the little bit of cleared space on Sans’s desk. His eyes roved slowly and luxuriously over the exposed form of his lover. The lab coat may be able to cover their back, but sitting on this desk with their legs splayed, everything was available for his greedy sight. He took in the pink tinting their skin and their eager nipples perked with the attention of the cold on Frisk’s exposed chest. Frisk shifted shyly as his eyes roamed lower over the pudge on their stomach and finally to the flush of color between their legs. He could already see the liquid accumulating there. His mouth watered at the banquet in front of him.

Frisk’s knees closed bashfully, and Sans’s eyes snapped back to their face. Nervous fingers fiddled with the cuffs of the jacket. Their face was red. “Stop...just staring.” They murmured, embarrassed. Sans felt his cock twitch in his pants. He tugged at the buttons of his shirt in an effort to get them undone. As the shirt fell open, he kissed Frisk quickly.

“don’t be embarrassed. i’m just takin’ in the sights.” Frisk cupped his jaw with both of their hands, and his whole being suddenly craved what would come next. Frisk kissed him as if he was the only thing that mattered in the universe. He could feel their love being poured into him, as if they could somehow push their entire soul into one kiss. It wasn’t quite enough, but at the same time too much. He wasn’t sure if his response was ever enough. If Frisk could ever feel how much he adored them. But still he made the attempt, trying to at least match them. 

He didn’t bother to hide his whimper as his heart was set alight. He yanked their hips towards him and pressed Frisk down onto the desk. Frisk made a small delighted noise as Sans shoved papers aside. He didn’t care if they were in the lab right now. He would be taking Frisk. He throbbed with need. He was certain Frisk knew what that kiss did to him. It was the most delicious torture.

He pressed rough sloppy kisses down their chest to latch onto a nipple. Their back arched with a cry as he bit a little roughly. “Sans!” They gasped, legs falling open for him again. Sans felt even more bolstered by the wetness on his stomach. He wanted to release himself from his no-longer-loose slacks, but he couldn’t remove his hands long enough to do so. Frisk rubbed themselves against him, whimpering at the friction as they pressed against the rougher fabric of his slacks. Sans shivered. Fuck, that was sexy. He could hear their voice echoing in the empty laboratory. Their nails bit into his back, adding a delicious pain to the mix. 

Sans inhaled the scent of sweat on their skin as he moved lower. He was certain that if he wanted to, he could push straight into them. But he was a good guy and, as much as Frisk didn’t seem to mind it being a little rough, he wasn’t going to risk hurting them. “Please please please please!” Frisk begged quietly the closer he got. Their bare feet caught on the edge of the desk, pushing their hips up.

Well, who was Sans to ignore such an honest invitation?

Sans gave a long luxurious lick to their most sensitive part, and Frisk all but sobbed. He did it again, enjoying the view. He loved seeing their gasps, feeling the heat of their arousal on his face. Not that it was his favorite place, but the noises Frisk made were too good to pass up. Nothing turned him on faster than seeing them lose control under his ministrations. They were such a quiet kid, but in moments like these they couldn’t seem to contain themselves.

He pressed two slicked fingers into them, making sure to distract and loosen them up with his tongue. Frisk keened softly. “S-Sans...!” He glanced up, knuckle-deep in them to see glossy eyes begging him. His knees were beginning to hurt from the hard floor, so he accepted the offer. He stood up, carefully twisting his fingers in them. They gasped, and Sans took advantage to press further in. He kissed their sternum before pressing a kiss to their lips, slowly beginning to move his fingers.

“god, you’re so hot.” He muttered. He curled his fingers, knowing he’d find their sweet spot right away. Frisk bit their lip as their hips jerked. The clenching around him made him groan. He was going to need new pants, he was certain.

“N-no more. Need you.” Frisk said. Sans pulled his fingers out, grinning at the sound of it. He could already tell that he wouldn’t last long. He only contemplated for half a moment before he flipped Frisk. They positioned themselves over the desk as Sans hurried to finally free himself. He kissed the dip in their back and lined himself up. Frisk spread their legs further.

“frisk.” He paused momentarily so that they would look at him. He kissed their shoulder blade lovingly. He couldn’t find the words he wanted to say. As much as he loved this human, he could never voice exactly how much. He wasn’t good at emotions. But Frisk seemed to understand from the tiny grin on their face. They grabbed his left hand and pressed a kiss to his ring. No more words were said on the matter, but Sans still felt something sad ache in him. He wished that he could just tell them. It seemed that at the most critical times he just couldn’t tell them–

Frisk’s hips tilted backward in encouragement. Sans pushed away his thoughts, understanding that he had other things to focus on. He spread Frisk just a bit more before he began to press in. He closed his eyes against the initial resistance, but Frisk was surprisingly pliant. Before he knew it, he was to his hilt. He groaned, not resisting the impulse to thrust. Frisk whimpered in pleasure.

Sans focused on the movements of their bodies together. Every thrust seemed to elicit a different sound from Frisk’s throat. Half-said words and broken thoughts. Words that no alphabet could form. Their nails dug into the desk as their hips moved with his. In the large room, their voices and the sounds of their lovemaking seemed extremely loud. He wondered idly if the door was locked, and if not, then who was here? Well they were in for an eyeful if they came in.

“O-oh god.” Sans grabbed at Frisk’s chest and pulled them a little more upright to try a new angle. Frisk lifted a leg, allowing Sans to be just a bit deeper. Shit, he was going to come. He bit a little roughly at Frisk’s neck and Frisk cried out. “Sans!” His hand slipped between their legs. He could feel himself entering them over and over again. He focused on helping them along. He needed them to come before him. He wanted to feel it again, the feeling of them pulsing around him. The first time had been addicting in a way he hadn’t expected. He needed to hold out.

“i’ve gotcha, frisk.” He panted even as his own whimper slipped through. Their hand joined his desperately. He could feel their edge building. Just a bit longer. “come for me, frisk. right here, right now.”

“Mine.” The word slipped from their lips, sending a thrill through Sans. “My Sans. Oh...!” And they were as lost as he was, slipping into his orgasm suddenly. He groaned into their back, hips pressing one last time and freezing as the sensations overwhelmed him. Their words echoed in his mind, and when he recovered enough, he didn’t bother to pull out right away. The bed was comfortable, but he didn’t feel sleepy. He needed to kiss them, though, so he made the effort to pull out. Frisk shivered, making Sans give a lazy grin.

When they rolled over to face him, the light of the lava lamp made the sweat on the body look beautiful. He reached forward to brush their hair out of their face to kiss them. Frisk smiled into the sweet kiss and Sans sighed in pleasure. Frisk held his hand pressed to their cheek, smiling softly. “Sans.” They whispered.

Sans wasn’t sure he would ever tire of hearing his name come from their lips. “yeah?”

They kissed his palm. “My Sans.” They murmured. There was a slight sadness in their look, alarming Sans a bit. “I wish...I could stay with you.”

“where are you goin’?” He asked, suddenly worried. They were still in their honeymoon state! Sans wasn’t due back to work for another week and Frisk didn’t have school for even longer!

“I can’t stay...I have to go back. You...know that right?”

“kid, what are you even talkin’ about?” He asked again. 

Frisk seemed even sadder. This was not the post-orgasmic bliss he had wanted. “I have...my own Sans to return to. This was fun...but I need to return to my Sans.”

“i _am_ your sans!” Sans said.

Frisk glanced at Sans’s hand, and Sans followed their look. He gasped in horror at the sight of bones (his whole hand was only bones!) before it was normal again. He tore his hand from theirs. They smiled some. “What’s the matter, Sans?” They asked with a small laugh. “Something get...under your skin?”

Sans woke up with his heart pounding. His body was damp and flushed in a way that he recognized. He felt like he’d just had a nightmare...but it had been so much better than that. He sat up in bed and grimaced at the feeling of his soiled pants. Well that was just great. Here he had been trying not to use the human Frisk as an excuse to jerk off, but the option had been taken from him.

He buried his face in his hands and laughed bitterly. His eyes watered some and he closed them against the onslaught of emotion. He had been so certain...so convinced that Frisk had been his. Not even taking into account the great imaginary sex he’d just had, he could remember the joy he felt at thinking Frisk was married to him. That he’d have them. That they weren’t from another universe where a different Sans was waiting for their return.

Sans gripped his hair and gritted his teeth. He was envious of the other Sans, and that was just crazy. He had a Frisk in this universe. But it wasn’t the same. He hated himself for giving into the urge to kiss them. He had never really been in love before, and now he had to go and fall in love with the one completely unavailable to him. It was pathetic. He should’ve taken the opportunity to tell them his feelings. Just so he could get rejected and get over it.

But Frisk wouldn’t have actually rejected him, would they? They would probably have smiled at him happily, if a little sadly, and kissed him goodbye. Why did it have to be goodbye, though?

He lifted his head and stared at his bare fingers. He wished that he could switch places with the other Sans...just for a little while. Just to hold Frisk one more time. It would be so simple to break his promise and go through the portal. Or even alter the machine so he could be in that world without switching with the other Sans. He wouldn’t mind sharing Frisk, so maybe he wouldn’t either? He never could ask Frisk if the other Sans had gotten angry. He doubted it, but he would never actually know.

He was being stupid. Sans took a deep breath and ran his hand through his hair. There was no point in thinking like this. “What if’s” never did him any good. He couldn’t just abandon his own universe. He had great friends and family here. He loved his life, even if there was currently a hole in his heart. He could put up with one of his best friends sounding exactly like the one he was aching to see. He wasn’t even envious of Asriel when he saw Azzy and Frisk get cozy together. He just longed for that connection. Because in his mind’s eye he could see the human Frisk with him. The two of them together on the couch during the holidays or on any other day. Frisk laughing at his stupid jokes and taking pictures on their phone to preserve memories. Being able to kiss them whenever he wanted. He could _see_ a life with the human Frisk.

And it was all being experienced by another Sans.

Sans scoffed at himself and climbed out of bed to strip off his clothing. He was done lingering on this. He would go take a shower and get his day started early. He left behind the ghost of a memory of Frisk in his bed, and wished quietly that he had built a time machine. Just so he could go back and spend time with them a little bit longer. Just...a little bit longer.


End file.
